More particularly, the manhole cover assembly of the present invention concerns a top frame adapted to carry a cover or lid and a bottom frame adapted to be supported on a base or foundation around a well opening, etc., and in which the top frame is provided with portion telescopically received in the bottom frame. The arrangement includes one or more locking means for securing the frames together in an adjusted position with respect to each other and the upper surface in which the manhole cover assembly is disposed.
In concrete manholes located in streets, pavements and other frequently trafficked areas, it is necessary that the cover be in an essentially flush condition with respect to the surrounding street or pavement surface, which requires the top portions of the manhole cover assembly to be adapted to the surface after the surface has been repaired or resurfaced.
It has been previously proposed to form the top frame of a manhole assembly as a lock ring or frame fitted in a recess in a bottom frame which is built-up in order to compensate for a rise in the level of the street or pavement surface which has been resurfaced. Such single rings or frames, however, make it necessary to adapt the surfacing material (or alternatively excavation of the material) around the manhole to compensate or orient the street surface with respect to the single ring or frame, or vice versa, which is not an acceptable economical practice.
It is also known to use telescopic top and bottom frames without using lock members so that the frames can be fixed with respect to each other. However, the plural frame arrangements known in the prior art, have drawbacks which improperly expose the upper frame to street servicing implements, such as snowplows or the like.